Material handling systems are frequently used in business and industry to transport materials from one location to another. Such systems typically include a delivery device for carrying the materials which are to be transported, and means defining a pathway along which the delivery device is adapted to travel. In addition, many material handling systems also include a central system control for controlling the operation of one or more delivery devices as they travel through the system, and for generally monitoring the condition of the system.
One known type of material handling system is a monorail material handling system in which the pathway defining means comprises an elevated track system, and the delivery device comprises a trolley having one or more drive motors thereon for propelling the trolley along the track system.
In known monorail material handling systems, the central system control is electrically connected to the one or more trolleys in the system by an electrically conductive track or bus incorporated into the track system thereof. The bus includes a plurality of separate conductors, and the central system control provides power (typically 240 volts A.C.) for powering the drive motors of the trolleys and control signals for controlling the operation of the trolleys via the bus. The central system control is connected to the bus by electrical wiring, and the trolleys include an arrangement of conductive collectors or brushes slideably engageable with the bus to maintain electrical connection therewith as the trolleys travel through the system.
In a large material handling system, the wiring connecting the central system control to the electrically conductive bus can be several hundred feet in length. This large amount of wiring requires a substantial investment in both installation time and material. In addition, the sliding electrical connections between the fixed bus and the brushes on the moving trolleys necessitate diligent monitoring and frequent maintenance to ensure reliable operation of the system.
Moreover, the electrically conductive bus, its attendant electrical wiring, and the high voltage power carried thereby present a substantial electrical shock hazard and prevent use of the system in many environments which require explosion-proof or fire-proof conditions.
Furthermore, in known monorail material handling systems substantially all system operations are controlled and monitored from the central system control as a result of which the central system control often requires a relatively expensive computer having a large memory capacity.